Preparation of clay catalysts



Patented, Apr. 1949 y UNITED STATES PATENT Hubert A. Shabakcr, Media, and George Alexander Mills, Ridley Park, Pa., and Ruth C. Denison, Wilmington, DeL, assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware No Drawing.

Application July 3, 1946,

Serial No. 681,426

I 9 Claims.

1 a The present invention relates to the treatment of natural clay substances and is chiefly concerned with the production of adsorptive and catalytic materials from such substances.

compounds in the clay to a form whereby-the Such removal may be effected without such accompanying removal of aluminum'compounds or other detrimental changes which reduce or de- In the preparation of certain clays for use as 5 stroy the adsorptive qualities of the product or decolorizing adsorbents and in catalysis it is'comreduce its catalytic activity. The, residual mass mon practice to activate the clay by subjecting acquires as a result of the treatment surprisingly the same to treatment with mineral acid. Such new and important properties particularly evitreatment extracts a large part of the aluminum denc'ed when a clay treated in accordance with compounds from the clay and incidentally also the invention and prepared asacatalyst is utilized removes a portion of the iron and/ or other fluxin hydrocarbon conversion, as will appear below. ing impurities therefrom. The products-obtained As a result of the treatment, raw clays having as a result of such treatment may be characteran iron content corresponding to as high as ized by reasonable catalytic activity and stability 4.% or more of R203 by weight can be reduced on continued service in commercial operation. generally to about 0.4% FezOs or lower and with However, in certain operations their stability is some clays to as low as 0.2 or 0.1% F6203. The less than desired. They still contain in most incatalytic or absorptive properties of many comstances a residual iron content that is not ormonclays heretofore regarded as inferior or undinarily removable by continued or more severe suitable for certain specialized uses named above acid treatment without extraction of too large a are so improved that these clays come into considquantity of the aluminum or impairment o'ther eration as inexpensive and eflicient materials for wise of the physical and other properties of the such purposes. Thus, many natural clays preresidue, particularly evidenced by a marked deviously regarded as inefiicient or undesirable as cline in catalytic activity. Although it is not dehydrocarbon conversionv catalysts are made suitsired to be bound by any scientific explanation, able for such use and otherwise catalytically acthere is reason to believe that the less readily tive or acid activable clays considerably improved removable iron components of clays are present in useful properties. in a different form from that ofthe more easily The treatment of the clay in accordance with I extractable iron components, being intimately as the present invention efiects a transformation to sociated in a complex with silicon or perhaps acid soluble salts of that portion of its iron conforming a part of the lattice structure by addition tent present in a form not selectively removable to or as proxy for other principal cations of the by acid treating, whereby it is made available for. pattern. This form of iron component may 'be subsequent removal such asby a mild acid leachbroadly designated as isomorphous, although ing and/or washing or in some instances by volait is recognized that the clay structure may not ti i a y e treatment with carbon disulnecessarily be crystalline and that portions or all fide at the spec fie high te p ot e of the more tenaciously held iron components 'wise not readily available and difiicultly remove may vary in form from that of the principal come n omp a ar tly converted toponent of the clay structure. salts which are quite soluble in acid solutions. In

In our. copending applications 644421 and 40 te f t t e y Set Out above, although it fi d January 30, 1946, of which the presis not desired to be bound thereby, there isreason ent application is in part a continuation, certain believe that the iron present as a Silicon 0 methods are described for the treatment of clays 1319K Otherwise forming a part of the lattice efiecting improvements in their properties par- Structure as addition to D 0 y or o e ticularly with regari to'their use as hydrocarbon as principal cations of the p s converted y cracking catalysts, such treatment comprising the i temperature 2 treatment to er contact with reactive gases r vapors at l t d or more reactive compounds such as sulfides temperatures, preferably in the range of from which are Soluble in e acid employed in 1200 F. and upward. Improvement in certain seq e ch properties of the clay isv already effected with The treatment with carbon disulfide at the hydrogen sulfide as the treating agent at even h temperature y pr y a w below 1200 F. 1 treatment of the clay with mineral acid or an The present invention is based upon the disorganic acid which forms soluble iron salts or covery thatby treatment of clays in dry form with complexes, including lower aliphatic carboxylic a. vapor or gas comprising'carbon disulfide t m acids such as oxalic and acetic as well as hydroxy peratures of at least 1300 especially improved acids including lactic and the so called sugar catalytic and absorptive properties are'imparted acids. Where the acid treatment precedes, the to theclays as hereinafter set. forth, These more available iron compounds (f..i., outside the changes .are accompanied by conversion of iron lattice structure) are removed as. soluble salts as in thek-nown acid activation of bentonites leaving the residual iron component (f. 1., chemically combined in the lattice) to be reacted with the carbon disulilde. Acid leaching following the treatment with the carbon disulflde containing gas or vapor, effects or facilitates the selective removal of products formed by the reaction of the carbon disulfide with the complex or otherwise less available residual iron components. It will be readily understood, therefore, that it may be desirable to employ an acid treatment before as well as after the treatment with the CS2 product. Instead of removing the freed or solubilized iron by acid or other solvent, it is possible to convert the same to vaporizable compoimds such as ferric chloride, and remove the same by volatization. Of course, this step, if practiced can also be followed by a subsequent acid washing step.

In the production of a catalyst, in accordance with the preferred embodiment, from a clay of the montmorillonite group or other clay having the characteristics of the bentonites or subbentonites, the initial acid pretreatment is particularly advantageous, since'the otherwise poor porosity of the natural or untreated clay impedes penetration by the carbon disulfide. Generally with kaolin type clays acid pretreatment is less significant although with some types of kaolin clays acid pretreatment may also be found beneficial. The acid treatment may be effected by known processes such as are employed in the as in the nature of a slurry, to which concentrated mineral acid such as hydrochloric or sulfuric is added, or dilute mineral acid may be added directly to the finely divided clay. In either case the ratio of acid to clay is preferably in the order of about 20 to about 40%. The initial acid treatment if practiced, is preferably efiected at elevated temperature as from about 160 F. to about the boiling point of the acid or acid-clay mixture, and may be continued for a period of about two to twelve hours; thereafter the treated clay is water washed and filtered. If desired, the clay may at this point be washed free of acid ions with accompanying extraction of soluble -metal salts. The acid treated clay with or without purification by washing may then be dried in any known 01" desired manner. More concentrated or larger proportions of acid may be employed and/or higher temperatures including increased pres- .sures, or longer periods of treatment up to .the approximate limit where the combined effect tends to no longer selectively remove iron compounds without undue solution of aluminum compounds. This point cannot always be defined accurately with respect to chemical composition of the acid treated clay, for the optimum point varies with the source of the raw clay. For many if not mostraw bentonites, however, this point is reached when'the weight ratio of SiOz to AlzOa of the total clay lies in the range of 2.521 to 10:1 for example about 4.5:1 and the residual alumina content is in the range of about 25 to for example about 17%. Acid treatments of clay such as for instance are described in U. S. Patents 1,397,113, 1,579,326, 1,642,871 'are suitable. The acid pretreatment, of course, may be less severe than is required for activation of the clay and may be sumcient only to open pores in the clay, allowing easy access of the carbon disulflde.

The untreated clay or the above described acid g-jgtreated clay or a commercially obtainable acid like (as is practiced in forming of clay catalysts) is subjected to the treatment with the Csz-containing vapor or gas at a temperature in the range of from about 1300 F. up to about the temperature which would result in rapid shrinkage orsubstantial incipient fusion of the clay. Since clays will vary in composition and properties including fusion temperature even when obtained from the same source, exact temperature ranges cannot beset out. It has been observed that with montmorillonite types of clay the maximum temperature may be as high as 1500 and at times 1550 F., whereas in the case of kaolin clays, even higher temperatures may be employed as above 1600 to 1650 F. The quantity of CS2 employed should be at least sufllcient to chemically combine with the quantity of iron present in the clay but is advantageously employed in excess. Any inert gas or vapor may be employed as a diluent or carrier for the CS2, or if desired other active non-oxidizing gases or vapors ad vantageously those containing combined sulfur, such as hydrogen sulfide, may be added to the CS2.

The iron compounds such as sulfides formed by the CS2 treatment may be removed by washing the treated clay product as with a solvent for such compounds, or preferably by treating with dilute acid, if desired alternated with water or solvent. The acid or solvent employed should advantageously have a selective action on the iron compounds formed by the CS2 treatment without removing substantial quantities of the aluminum or silicon components of the product. Instead of leaching or wet extracting the freed iron compounds, they may be converted by further treatment with an appropriate reagent to a vaporizable compound, such as ferric chloride which is removed by vaporization. In some instances and with some clays it will be found advantageous to subject the clay to intermediate oxidizing conditions following the treatment with CS2, which may be accomplished by subjecting the clay to hot air at a temperature of 800-1000 F. or less. In'this manner the subsequent leaching by acid or solvent may be facilitated.

To obtain the beneficial advantages of the present invention it is essential that the treatment with carbon disulfide be carried out at temperatures of about 1300 F. or higher, since at lower temperatures the tenaciously bound isomorphous iron compounds are not sufficiently released and the resulting products do not possess the described important properties of catalysts prepared in accordance with the present invention. The desired modification of the clay and transformation of the iron by the CS2 can be effected in short time as of the order of several minutes, far less than an hour being usually required even at the lower temperatures of the described range.

Depending upon the use to which the clay is to be put, the preliminary acid treatment and/ or the CS2 treatment may be carried out with the clay in finely divided form or as preformed aggregates of larger size which may be broken pieces of filter cake or more regular and uniform shapes. In

area-,0

for instance by compressing the dry finely divided particles orv powders as in a pelleting machine or by previously wetting the dry, treated or untreated, clay with water or other inert liquid that will bind the small particles or powder into a cake which, after drying, can be broken up into granules'or fragments of desired sizes or the wet mix can be formed into more regular shapes by molds ing including casting, extruding or the like. In instances where the described high temperature CS: treatment is carried out on powder or fine particles, the cohesive properties of the clay "may be afiected, in which case it may be necessary to add a suitable binder or. lubricant to assist in the forming operation, carebeing taken in selecting such ingredient and maintaining the addition at a gninimum so as not to interfere with the catato catalyst as those set out above in connection v .gasoline or naphtha fraction under conditions lytic activity of the'formed mass, as for instance I one can use a raw or acid activated clay of good cohesive properties as a binder for the treated clay. If the clay product isto'be' employed'as' catalyst or otherwise in the form of fine particles or powders, the formation of larger aggregates such as granules, tablets or pellets for treatment with CS: isof course not necessary, but if desired, such larger masses can be formed and treated in accordance with the above-described procedure and subsequently ground or comminuted to the required fineness.

For catalytic use it will be found advantageous as a final step in the preparation of the contact mass from clay to subjectthe same to calcin'ation at-a temperature above 800 F. in air with or without added steam or steam alone.

As a result of the improvement obtained by the described process of the invention, the choice of raw clays for many industrial uses is materially extended. Thus, it is made possible in accordance with the present invention not only to obtain im proved catalysts from hitherto employed active clays such as. montmorilloni-tes including acidactivated bentonites and the like, but by the herein disclosed novel processes, clays such as those of the kaolin type which could not be brought to acceptable levels of catalytic activity by prior art methods, now become available for practical use as hydrocarbon conversion catalysts.

For use of the contact masses preparedby the -present invention as catalysts in hydrocarbon conversion processes no change inconditions of treatment of the hydrocarbon to be processed is rendered necessary. The usual conditions as to time, temperature, etc. can be followed if desired. As an example of a fixedor stationary catalyst bed operation, cracking may be carried out at a temperature of 800 F. to 900 F., employing a space rate (volume of charge, liquid basis, per volumeof catalyst per hour) of about similar to those employed in crackihg. In all of these processes, the catalyst after use is regenerated by contacting it with air or other oxygencontaining gas to burn ofl carbonaceous deposits. In the following examples, notations of catalytic activity are expressed in terms of the standard test (CAT-A method) described in Laboratory method for determining the activity of cracking catalysts" by J. Alexander and H. G. Shimp, page R-537. National Petroleum News, Technical Section, August 2, 1944. In accordance with the method, a light gas oilis contacted witnthe cata lyst under fixed cracking conditions and the activity of the catalyst is designated in terms of volumeper cent of obtained gasoline; the weight per cent of wet gas, specific gravity of the gas, and'weight per cent of carbonaceous deposit are also determined.

' Example I The raw clay treated in the several preparetions of this example was a kaolin, obtained from a deposit on the Eccles property in Putnam County, Florida, having the following compositionon an (a) The clay was worked in water to obtain a plastic mix suitable for extrusion and'ext'rude'd to form 4 mm. cylindrical pellets which were dried in an oven over a temperature rangeof 130 .F. to 240 F.- for three hours.

(b) Dry'pellets from (a) wereheated to 1400 F. in an electric furnace and treated at this temperature for two hours with a flowing stream of nitrogen towhich carbon disulflde was added continuously until the total -CS2 employed was equal to about 9.0 per cent of the weight of'the pellets, (being in stoichiometric'excess of the'iron content). The nitrogen gas flow was then con tinned for about 2 hours longer, heating being stopped, then'the flow of gas discontinued and Y the pellets-permitted to cool to room temperature 1.5, and a pressure of about 15 pounds per square inch gauge. The temperature, of course, may be varied within the range of about 700 F. to 1100" F., the space rate within the range of about 0.5 to about 8, and pressures maybe employed from about atmospheric or slightly lower up to-about 100 pounds per square inch, or even higher. Under these conditions the operating period on stream may range from five to sixty minutes,

for example 10 to 30 minutes alternating with regeneration periods.

In processes other than those where the-catalyst remains in a stationary or fixed bed,f such as where the catalyst moves through the reaction zone, the conditions employed may be such, as to subject the oil to substantially equivalent con ditions including contact time and ratios of oil and discharged.

(c) The cooled pellets from (b) were then treated with an equal volume of 15% hydro chloric acid solution (15 parts by weight HCl to parts H20) and permitted to stand for four hours, after which the acid was decanted and replaced byan equal volume of fresh 15% hydrochloric acid solution. The pellets and acid solution were permitted tosta'nd in contact for an.

additional 20 hours with occasional agitation, after' which the acid was discharged. The pellets were washed with water until the wash water tested free of chlorides, then dried in an oven at about 200 F. The dried pellets were finally calcined in air at 1050 F. for 2 hours.

(11) Another portion of the pelletsfrom (a) above were contacted with CS2 in nitrogen at 1300" F. .(abouttwice the previous quentityjof ignited basis (containing 10-20% amaoaa CS2 being employed) then iurther treated in the same manner as the 1400 F. pellets in (b) and (c), above.

(e) For comparison, similar'treatments with CS2 were conducted on like pellets at lower temperatures as will appear in the tabulation below. The pellets obtained in each instance were analyzed for iron content with the following results:

C: treat temperature 1400 F. 1300" F. 1200 F.

Per cent F020; 0! calcined clay weight basis 0.10 0. 45 0. 90

Example I! The raw clay employed in this example was a kaolin from Putnam County, Florida, known commercially as Edgar E. P. K, having the following analysis on an ignited basis:

vantageous for use in treating such stocks.

Parts by weight 8102 53.0 A1203 414.2 F8203 1.14 CaO 0.50 MgO 0.26 T102 0.40 Alk. metal (as oxides) 0.5% I

Pellets were prepared from the Edgar clay in the same manner as in la above and the pellets similarly treated with CS2 in nitrogen at 1400 F. for 2 hours, acid leached and finished as in 1b and I0.

The pellets on analysis were found to contain 0.28% F8203. The same clay pellets similarly treated with CS2 at 1200 F. for two hours and leached still contained 1.09% FezOz.

Example III A commercial acid-activated sub-bentonite clay was pelleted as in the preceding example and likewise subjected to treatment with CS2 in excess of the calculated amount necessary to react with the iron content, acid-leached and finished as above described in Example I.

The clay pellets which had originally an iron content of about 2% FezOa, after treatment at 1300 F. with CS2 showed the presence of 0.32% F8203, while after similar treatment at 1200 F., there still remained 1.15% FezOa.

Example IV CS: Pclleted clay treated g 8 at F. 1

"Eccles" kaolin 1, 300 0. 45 l, 200 0. 90

"Edgar EPK" l. 400 0. 20

Commercial acid-activated clay l, 300 0. 32 l, 200 l. 15

In cracking and reforming of ordinary petroleum stocks, catalysts prepared from commercial In many instances, particularly with kaolin clays, the general catalytic activity and efllciency of the clay is also materially improved by the described high temperature treatment with CS: and leaching, as is evident from the following comparison of samples of pelleted clays finally calcined in air at 1050" F. for 2 hours:

CAT-A Yields t t Clay Gasor?" 313i g;

g h percent percent ar tilt at 2-:

r n 1, 4 33. 5 2. 9 8. 2 1.42 EPK 1,200 29.5 2.3 1.4 1.34

Surprisingly, in many instances a clay having an activity so low so as to be valueless for commercial use can be brought in accordance with the invention to acceptably good activity level, as is typified by the above Edgar EPK which has an activity when not so treated of only about 11% gasoline being pelleted and calcined in air under the same conditions as the catalyst of the above table.

It 'will be noted that in accordance with the preferred embodiment of the invention as set out in the above specific examples, a heated, inert, non-oxidizing gas, such as nitrogen is employed as adiluent and carrier for the active carbon disullide vapor. of using an inert gas or vapor to preheat the clay and/or as a carrier for the active treating gas or vapor is not limited to processes in which the active treating gas comprises carbon disulfide, and may be employed with other active gases or vapors, such as hydrogen sulfide gas or vaporized sulfur, as the reagents for reaction with the iron components of the clay.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims. Hydrocarbon conversion processes employing catalytic contact masses that may be prepared in accordance with the present, invention are particularly claimed in our copending applications Serial Nos. 644,425 and 644,426 filed January 30, 1946.

We claim as our invention:

1. The method of preparing adsorptive contact masses which comprises the steps or subjecting clay to the action of carbon disulflde at a temperature of at least 1300" F. but below the temperature of substantial incipient fusion of the clay, and leaching the thus sulfided clay with an acid.

2. The process in accordance with claim 1 in which the clay is a sub-bentonite.

The described feature leaching the sulfided clay with diluted mineral acid.

6. The method of preparing catalytic contact masses of low iron content which comprises forming a clay material containing iron compounds into pellets, subjecting the pellets to a heated gaseous atmosphere comprising carbon disulfide vapor, at a temperature of at least 1300 F. but below the temperature of substantial incipient fusion of the clay, to form sulfides with iron compounds in the clay and removing the formed sulfides of iron.

'7. The method of preparing a contact mass of low iron content from a clay material containing iron to an extent of more than 1% F820: which comprises, subjecting the said clay to mild acid treatment, to remove at least a portion of the available iron compounds, converting iron compounds remaining in the residue to sulfides by contact with a gas containing vaporized carbon disulfide at a temperature of at least 1300 F. but below the temperature of substantial incipient fusion of the clay, and removing the formed iron sulfides by acid leaching.

8. The method of activating kaolin which comprises treating the same with carbon disulflde at a temperature of approximately 1400 F., acid leaching the sulfided product, and calcining the residue.

9. The method of preparing a clay catalyst of low iron content which comprises the steps of acid treating an iron-containing clay to an extent at least suflicient to improve the porosity thereof and insuflicient to reduce the alumina content thereof tobelow 10%-by weight of the clay, washing and drying the acid-treated clay, subjecting the dried clay to contact with carbon disulflde in stoichiometric excess of the iron content of the clay and at a temperature of at least 1300 F. but below that causing substantial incipient fusion of the clay, to transform the major portion of the iron compounds present to iron sulfides, leaching the sulfided clay with dilute mineral acid, then washing, drying, and calcining the purified clay product.

HUBERT A. SHABAKER. GEORGE ALEXANDER MILLS. RUTH c. DENISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

